/*
 * Copyright 2002-2007 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core;

import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

/**
 * ParameterNameDiscoverer implementation that tries several ParameterNameDiscoverers
 * in succession. Those added first in the <code>addDiscoverer</code> method have
 * highest priority. If one returns <code>null</code>, the next will be tried.
 *
 * <p>The default behavior is always to return <code>null</code>
 * if no discoverer matches.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @since 2.0
 */
public class PrioritizedParameterNameDiscoverer implements ParameterNameDiscoverer {
	
	private final List parameterNameDiscoverers = new LinkedList();


	/**
	 * Add a further ParameterNameDiscoverer to the list of discoverers
	 * that this PrioritizedParameterNameDiscoverer checks.
	 */
	public void addDiscoverer(ParameterNameDiscoverer pnd) {
		this.parameterNameDiscoverers.add(pnd);
	}


	public String[] getParameterNames(Method method) {
		for (Iterator it = this.parameterNameDiscoverers.iterator(); it.hasNext(); ) {
			ParameterNameDiscoverer pnd = (ParameterNameDiscoverer) it.next();
			String[] result = pnd.getParameterNames(method);
			if (result != null) {
				return result;
			}
		}
		return null;
	}

	public String[] getParameterNames(Constructor ctor) {
		for (Iterator it = this.parameterNameDiscoverers.iterator(); it.hasNext(); ) {
			ParameterNameDiscoverer pnd = (ParameterNameDiscoverer) it.next();
			String[] result = pnd.getParameterNames(ctor);
			if (result != null) {
				return result;
			}
		}
		return null;
	}

}